The present invention relates to paper-making machines in general, and more specifically to a novel stock inlet arrangement for such a paper-making machine. Still more particularly, the invention is directed to a stock inlet arrangement providing an improved stock distribution for the paper stock that is directed to the slice and there ejected onto a forming wire.
In paper-making machines it is usually essential that the dilute paper stock suspension be as homogenous as possible as it flows to the slice, and that it be flowing at uniform velocity and direction when it is spread onto the forming wire. Unless these requirements can be met, the finished paper will have undesirable variations in its properties, for instance in the form of streaks, in the form of areas in which the fibers are light or sparce, in variations in the sheet strength, and other problems.
Various proposals have been made in the prior art to meet these requirements. One of these involves an apertured distributor roll upstream of the slice. However, rolls of this type will themselves contribute to the development of certain non-uniformities, and it has been found that quite frequently the sheet product will have streaks as the result of eddies passing through the roll or wakes which are created behind the roll as the latter rotate it.
Another approach involves the use of stock distributing pipes which are designed as diffusers. However, because of the use of these pipes the flow path of the paper stock suspension is considerably increased and it has been found that this leads to a flocculation of the fibers. This prior-art construction proposes to employ a flow channel which extends over the width of the machine and is interposed between the distributing pipes and so-called fine pipes. The distributing pipes supply paper stock into the flow channel and from there it must change its flow direction to enter into the fine distributing pipes which supply it to the slice. This results in the production of uncontrolled eddy currents in the flow channel and leads to faulty fiber distribution within the suspension, with a consequent development of the problems that have been outlined earlier.